This invention relates to the sensing of the density of rod-like material and to the controlling of the density thereof, and especially in the field of textile fibers this invention particularly relates to sensing the density of slivers produced by textile machines and to the controlling of the sliver density by controlling the input speed of the machine.
While the invention is particularly described below relative to a carding machine or card, it will be appreciated that the invention extends to other types of textile processing equipment, such as drawframes and pin drafters, which also produce slivers.
As above-indicated, besides relating to the sensing of sliver density, this invention also relates to the controlling of that density, i.e., to the automatic leveling of the density of the sliver produced by a textile machine or to rod-like material produced by other machines such as cigarette making machines. Automatic sliver leveling equipment for cards and other textile machines and machines in other fields are in general well known and are frequently referred to as "autolevelers." For example, the Zellweger Ltd. Company of Uster, Switzerland advertises a card sliver leveing device under the name "Uster's Control Card System," with an indication that sliver weight never exceeds .+-. 2%. Used in such systems to measure the cross-section of the sliver is a pneumatic sensing trumpet or funnel-shaped nozzle such as shown in the Uster British Pat. No. 1,137,297 and also in U.S. Pat. No. 3,435,673 granted Apr. 1, 1969. Those patents review many of the prior art ways of sensing variation in the substance cross-section of textile material, slivers in particular, and of course describe in detail the Uster pneumatic way of measuring sliver cross-sections. Cross-sectional measurement by such prior art does in fact appear to measure sliver density effectively, or sliver weight if the thickness is held uniform. For reasons stated in those patents, the various measuring systems prior to the pneumatic measuring system have disadvantages and obviously so does the latter, which it is an object of the present invention to obviate.